JPS60184860A - Thermal head driving system - Google Patents

Abstract

PURPOSE:To control the heating level at a high speed with a high accuracy by regulating driving conditions of driving signals according to information to be recorded while the temperature of a heat generating body at the start of recording is controlled to be a specified value. CONSTITUTION:When a data latch signal DL is inputted, a latch circuit 61 memorizes a contrast data Dn temporarily. A recording signal generation circuit 62 into which are inputted a line timing signal LT, a clock signal CL and output information of the latch circuit 61 outputs a recording signal with the pulse width corresponding to the contrast data Dn to a heat generating body driving circuit 65. The first temperature compensation signal generation circuit 63 into which are the line timing signal LT, the clock signal CL and the output information of the latch circuit 61 outputs a heating variation compensation signal for compensating for variations of heat storage of a heat generating body due to changes in heating level to the heat generating body driving circuit 65. A starting signal ST is inputted into the second temperature compensation signal generation circuit 64 at the start of the equipment or the turning of pages and it outputs a startup temperature compensation signal to the heat generating body driving circuit 65.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a driving method for a thermal head, and more particularly to a driving method that can accurately control the amount of heat that a thermal head supplies to an object to be heated.

fb) Technical Background There are two types of thermal printers that use heat to record information such as characters: a thermal recording method and a thermal transfer recording method. The former is a method that records by bringing the thermal head into direct contact with the recording paper, which changes color due to heat, and heating the heating element of the thermal head to change the color of the recording paper.The latter uses the thermal head to heat the ink and melt or sublimate it. This is a method of recording by transferring it onto recording paper. Furthermore, based on the heating element scanning method, there are two main types: line recording method and serial recording method. A line recording method is used for high-speed recording, and a serial recording method is used for low-speed recording.

FIG. 1 shows an outline of a line recording type thermal transfer recording apparatus, and FIG. 2 shows the structure of a thermal head.

The thermal head 11 has an ink sheet 12 and recording paper 13
It faces the platen 14 via. Inksey eyes 2
is heat-fusible, and by heating the second ink sheet 12 with a thermal heater 11, the ink sheet 1
The ink No. 2 is melted and transferred onto the recording paper 13 to perform recording. The thermal head 11 has heating elements for one line arranged along the direction perpendicular to the plane of the paper, and records for 1947 minutes are performed almost simultaneously. When 1947 minutes of recording is completed, the recording paper 13 and the ink sheet 12 are simultaneously transported in the direction of the arrow.

The thermal head 11 has a multilayer structure as shown in FIG. That is, a glaze layer 24, a heating element 23, and an electrode 22 are provided in a layered structure on a substrate 25, and two protective layers are provided on the surface that contacts the recording paper.

Note that 26 is a heat sink.

(cl. Conventional technology and problems Such thermal heads accumulate heat within them.

However, as shown in FIG. 3(a), the temperature of the heating element at time t1 when the drive signal Pa with the pulse width Ha is applied is Ta, and the pulse width Wb (as shown in bl)
The temperature when applying the drive signal I)b with Wb<Wa) is T
b (Tb<Ta), and as shown in (C), when a drive signal Pc with a pulse width IAc (Wc<Paint) is applied, the temperature becomes Tc (Tc<Tb). That is, the temperature T of the heating element at time t1 varies greatly depending on the amount of heating (corresponding to the pulse width of the drive signal) applied to the heating element.

This is a change in heat storage in the heating element due to a change in the amount of heating. Furthermore, even when a drive signal Pc with a pulse width We is applied, the temperature at time t1 is TC, but at time tll the temperature becomes Td (Tel < Tc), and the temperature of the heating element changes depending on the elapsed time from the start of recording. different. This is a heat storage fluctuation in the heating element due to a change in the recording cycle.

In this way, since the initial temperature of the heating element is different, if we consider the time when a drive signal with a predetermined pulse width is applied in the next recording cycle, the temperature characteristics of the heating element will differ depending on the driving conditions of the past drive signal, and the heating element cannot be controlled to a desired temperature.

To deal with this, detect the temperature of the thermal head,
It is conceivable to feed back the detected temperature and change the drive conditions (pulse width, wave height, etc.) of the drive signal applied to the heating element (hereinafter referred to as the feedback method).
However, such a feedback method cannot completely correct changes in recording density due to heat accumulation. In other words, heat storage can be broadly classified into those caused by the thermal head substrate, etc., and those caused by the glaze layer, but heat accumulation in the substrate changes at a slow rate with respect to the recording cycle, so it can be corrected by the feedback method described above. . However, the M heat generated by the glaze layer changes rapidly with respect to the recording period. Therefore, it is virtually impossible to correct heat accumulation due to the glaze layer using the feedback method.

Conventionally, for this purpose, attempts have been made to control the applied power of the next recording pulse signal based on the temperature history of the temperature at which the heating element was subjected to recording in the past (this is called the temperature history method). .

Taking binary recording as an example, if the previous recording was black, the power supplied to the heating element could be reduced by shortening the pulse width or reducing the pulse height of the drive signal applied to the heating element compared to when it was white. This method reduces the

As described above, by adopting the temperature history method, it is possible to reduce changes in recording density due to heat accumulation in the thermal head, but it has the following drawbacks. In the temperature history method, by applying past drive conditions to a theoretical formula for heating and cooling characteristics, the temperature of the heating element at the start of the next recording is determined, and the drive signal conditions corresponding to the amount of heat to be supplied are determined from this temperature. This is essential. This calculation requires complex calculations such as exponential functions, and all heating elements installed in the thermal head (for example, if the recording paper is A4 size,
8 dots/mm, 1680 heating elements are required), and a circuit capable of high-speed calculation is required.

Further, the larger the number of traced histories, the more the error in recording density due to heat accumulation can be reduced, but the more traced back the history, the longer the time spent on the above-mentioned 81 calculation becomes.

Furthermore, in order to increase the recording speed and to limit instantaneous power consumption, the recording cycle of the heating element is not constant, and in order to calculate the drive signal conditions from the past drive conditions, it is necessary to take into account changes in this recording cycle. It is also necessary to take these factors into consideration, which complicates calculations and results in a huge variety of combinations of driving conditions.

These drawbacks are inconvenient for improving recording speed. Since the next drive signal cannot be applied until the above calculation is completed, the recording cycle is substantially reduced. It also requires a high-speed and high-precision arithmetic circuit.

(dl Purpose of the Invention The present invention focuses on this point, and eliminates the accumulated heat without performing calculations to compensate for the change in recording density due to the heat accumulated in the thermal head prior to application of the next drive signal. The present invention provides a thermal head drive method that can control the amount of heating at high speed and with high precision by compensating for temperature changes in the heating element caused by the heat generation.

(el) Structure of the Invention In this invention, heat storage fluctuations that occur during each recording period are canceled within that recording period so that the influence of heat storage fluctuations does not affect the next recording period. By controlling the temperature of the heating element to a constant value at a certain time from the start of recording, the temperature history of the heating element is erased, and subsequent temperature characteristics of the heating element are independent of heat storage. Furthermore, in response to changes in the recording cycle, the temperature of the heating element at the start of the next recording can be adjusted by controlling the drive conditions of the drive signal according to the time from the fixed time to the start of the next recording. By setting the value to a constant value, it is possible to make changes in the heat storage of the heating element due to changes in the recording cycle unrelated to subsequent temperature characteristics of the heating element.

In this way, the temperature change due to the difference in the amount of heating to the heating element and the temperature change due to the change in the recording cycle are canceled out within the recording period, thereby making the temperature of the heating element at the start and end of recording the same. This eliminates the need to refer to past driving conditions at all.

To this end, the present invention provides a thermal printer that performs recording by heating a heating element using a drive signal, in which the drive conditions of the drive signal are defined by the information to be recorded, and
This is characterized in that the temperature of the heating element at the start of recording is controlled to a predetermined value.

(G) Embodiments of the Invention Below, embodiments of the or-marhenode drive system according to the present invention will be described in detail.

How to control the temperature of the heating element as described above 11.7
There are two types of ξ: one that performs auxiliary heating and one that does not perform auxiliary heating, but first we will describe a method that performs auxiliary heating.

FIGS. 4 and 5 show time-temperature characteristics and drive signal waveforms for detailed explanation of the present invention.

In FIG. 4, when a recording signal Pa having a pulse width IAa as shown in (a) is applied to the heating element, the temperature of the heating element changes as indicated by A, and at time L1 the target temperature Ti
is equal to When a recording signal pb having a pulse width Wb as shown in (b) is applied, the temperature of the heating element changes as shown in B, and at time t1 the temperature becomes less than the target temperature Ti, so at time tb A temperature compensation signal Pbl of the pulse width meter 1 is applied. This allows the temperature of the heating element at time tl to be Ti even when the recording signal pb is applied. In addition, a pulse width Wc as shown in +c+
When a recording signal Pc is applied, the temperature of the heating element is changed to T at time L1 by applying a temperature compensation signal Pb2 having a pulse width Wcl at time tc as shown in C.
It can be i.

Here, the pulse width of the recording signal Pa-Pb-Pc is defined by the gradation level of the information to be recorded,
The temperature compensation signal Pbl - Pcl compensates for fluctuations in heat storage in the heating element due to changes in the amount of heating the heating element is heated by the recording signal as well as changes in the gradation level. Therefore, this temperature? ili l award signal pb1 ・Pb2
is referred to as the heating change compensation signal.

The pulse width of the IJU thermal change compensation signal 1'bl-Pb2 can be defined by the gradation level.

As described above, heat storage fluctuations in the heating element due to changes in the amount of heating can be compensated by the heating change compensation signal Phi ・Pc,1, but heat storage fluctuations in the heating element due to changes in the recording cycle can be compensated for by the drive signal Pbl ・Pcl. cannot be compensated by. Therefore, as shown in Figure 5, the next record is the time (
1 and is delayed until time t3 or time t5, temperature compensation signals Px and Py are applied. However, when the start of the next recording is delayed until time t3, by applying the temperature compensation signal Px of pulse width waste X at time t2, the temperature of the heating element can be adjusted to match the target temperature Ti at recording start time t3. -I can. Similarly, when the start of recording is delayed until time L5, by applying the temperature compensation signal py with a pulse width toy at time t4, the temperature of the heating element can be made to match the target temperature Ti at recording start time L5. The driving signals Pb1 and Pcl applied at time ti are the same as the heating change compensation signals Pbl and Pcl shown in FIG.

This temperature compensation signal P/py is for compensating for heat storage fluctuations in the heating element due to changes in the recording cycle, and is called a period change compensation signal in contrast to the heating change compensation signal that compensates for changes in the amount of heating. 9. This periodic change compensation signal Px
The pulse width of -Py is defined by the time from time t1 to time t3 or t5 when the next recording starts.

Next, an example will be shown in which the recording cycle is fairly constant and the influence of changes in the ambient temperature of the ink sheet and the ambient temperature of the heating element of the thermal head can be ignored or separately corrected.

Figure 6 is a block diagram showing an overview of a device for compensating for heat storage fluctuations in a heating element caused by changes in the amount of heating, Figure 7 is its detailed circuit diagram, and Figure 8 shows the main parts of Figure 7. The signal waveform is not shown and the time chart is from 1 onwards.

In the sixth section, 61 is a latch circuit, 62 is a recording signal.
63 is the first temperature compensation signal generation circuit,
64 is a second temperature compensator (1N signal generation circuit, 65 is a heating element drive circuit. The launch circuit 61 is manually supplied with a data latch signal 1) and gradation data 1), and a data latch signal 1) 1) ．． When manually operated, the launch circuit +1L temporarily stores the gradation data Dn. The line timing signal LT, clock signal CL, and output information of the latch circuit 61 are input to the recording signal generation circuit 62.
2 outputs a recording signal with a pulse width corresponding to the gradation data On to the heating element drive circuit 65. The first temperature compensation signal generation circuit 63 is manually supplied with the line timing signal LT, clock signal C1, and output information of the launch circuit 61, and can detect heat storage fluctuations in the heating element due to changes in the amount of heating. ili
A heating change compensation signal for transmission is output to the heating element drive circuit 65. A start signal ST is inputted to the second temperature compensation signal generation circuit 64 at the time of starting up the device or changing a page, and outputs the temperature compensation (R month) to the heating element drive circuit 65 at the time of start-up.

Although not shown, the body drive circuit 65 is connected to one heating element of the thermal head. Therefore, the block 60 indicated by the dotted line corresponds to one heating element, and when the thermal head has 1680 heating elements, the block 60
requires 1680 (llil.

In FIG. 7, read-only memories (hereinafter referred to as ROMs) 70a, 70b, and 70c each store various information corresponding to gradation data Dn. ROM
The pulse width information of the recording signal is stored in the ROM 70a, the time from the end of heating by the recording signal to the start of applying the change compensation signal is stored in the ROM 70c. The pulse width information of the heating change compensation signal is stored.

The latch circuits 61a-61b and 61c are each RO
The output of M 70a-ROM 70b-ROM 70c is temporarily stored, and it is the data latch signal r.
This is done each time the file is entered. counter 71a
・71b ・71C has line timing signal LT at terminal 1. The latch circuit 61a・etb
・Output 1 of 61c? j information is input from terminal DT, and clock signal 01.j is input from terminal DT. Each time , the read value is subtracted. When each of the counters 71a, 71h, and 71c finishes subtracting the read values, it outputs a carry signal from the terminal CY to the corresponding OR game 1-0RI, OR2, and 0r13. The output of each methi gate 0 old ・0]n 2 ・01n 3 is a flip-flop circuit (hereinafter referred to as FF)
It is input to the R terminals of 72a, 72b, and 72c. The FF 72a receives a line timing signal q1. r is input to terminal C, and when a signal is input to terminal C, terminal Q becomes "1" and the terminal prize becomes "Oo".

The output terminal direction of PI' 72a is connected to terminal C of FP 72b, and by inputting a signal to terminal R, the terminals become "1" and the terminal Q becomes '0°.PI'
The output terminal γ of l'F'72b is connected to the terminal C of 72C, and by inputting a signal to the terminal R, the terminal
◇(The value becomes 1°, and the end 7'-Q becomes 0'.

ORGATE) 174 has PF 72a-I'P 72c
Terminal Q of is connected. Furthermore, or game 1-(ll
? 4 includes a monostable multi-high break circuit (hereinafter referred to as "interval") 64a forming a second throat temperature compensation signal generation circuit 64;
output is connected. The MM 64a outputs a startup standby temperature compensation signal S1 having a predetermined pulse width each time the startup signal ST is input manually. The output of OR game 1-0R4 is connected to the gate terminal of transistor Tr. The source terminal of the transistor Tr is grounded via one heating element 73 of the thermal head, and its train terminal is connected to the power supply Vc.
connected to c.

Next, the operation of the circuit shown in FIG. 7 will be explained along the time chart shown in FIG. First, when the start signal ST is input,
The MM 64a outputs a startup standby temperature compensation signal S1 whose output is 1'1 for a certain period of time.

On the other hand, the activation signal ST is an OR gate ORI ・01?2
・PF 72a ・72b ・72c via 0113
and reset each pp. The start-up temperature compensation signal S1 having a pulse width between the pulse widths drives the transistor Tr via the OR gate OR4, and heats the heating element 73. Is the pulse width WO the startup temperature? li (Heating by the R signal St is completed, and the temperature of the heating element 73 is set to Ti at the recording start time t1.

Next, when the line timing signal LT is input, the output information of the launch circuits 61a, 61b, and 61c are sent to the number J counters 71++, 71b, and 71c. On the other hand, in IiF 72a, line timing signal 1. Its state is inverted by the input of T, and the terminal Q
The output of is ′l゛. I wanted to-ζ, counter 71
Since the terminal UN of a becomes .degree.l', the counter 71a starts subtraction in response to the clock signal CL. However, since the terminals [N of the counters 71b and 71c are "0°," the argument operation does not start. When the count value of the counter 71a becomes "0" and a carry signal is output from the counter, the FP
72a is inverted and its terminal Q becomes "0".

The signal S2 from the FF 72a is a recording signal whose pulse width Wl corresponds to the gradation data Dn, and by driving the heating element 73, the ink of the ink sheet I is melted and transferred onto the recording paper. Recording is performed by

When the state of PF 72a is reversed, the counter 71
Since the terminal +V of 1) becomes Bi, the counter 71b starts subtracting the value from 7 to 1.

When the d1 value of the counter 71h becomes °()°, Fp7
Since the state of FF 2b is inverted, the terminal C of FF 72c becomes "l". Therefore, its output terminal Q becomes '
1°, and the counter 71c starts subtracting.

When the count value of the counter 71c reaches 0°, the FF 72c
The state of FF 72c is reversed, and its output terminal Q becomes "Oo."In other words, the output S4 of FF 72c is
It is a heating change compensation signal that becomes 'l' during the time when is performing a subtraction operation, and its pulse width -2 is defined by the pulse discount of the recording signal S2, in other words, the specified gradation data I]n . Heating change compensation signal S4 OR gate OR
4 to drive the transistor Tr to heat the heating element 73. Is this heating change compensation signal S4 so that the temperature of the heating element reaches the target temperature Ti at time t2 when the next line timing signal LT is input? Ili will be compensated.

The next line timing signal LT is input at time t2,
If the level of the gradation data Dn instructed at that time is lower than the level of the gradation data of the information recorded immediately before, the pulse width of the recording signal S2, which is the output of the FF 72a, will be Wll, which is smaller than the width of the FF 72a. . For this purpose, the heating element 73
The temperature is low, and the pulse width W21 of the heating change compensation signal S4 to match the target temperature Ti+ is set wider than U2. That is, the heating change compensation signal S4 having a pulse width of 2·W21 compensates for changes in the pulse width of the recording signal applied to the heating element 73, in other words, heat storage fluctuations in the heating element due to changes in the amount of heating to the heating element. As shown in FIG. 8, the line timing signal L'r is
In the case where the recording period does not change, in other words, the heating change compensation signal S4 cancels the heat storage fluctuation of the heating element caused by the change in the amount of heating to the heating element, and the heating element at the start of recording is temperature can be maintained at target YM, degrees Ti. However, for an apparatus in which the recording cycle varies in various ways, this heating change compensation signal Lj cannot maintain the temperature of the heating element at a constant target temperature Ti at the start of recording.

Figures 9 to 11 are circuit examples for this purpose, and the MP of the heating element due to changes in the amount of heating! ) and to compensate for fluctuations in the heat storage of the heating element due to changes in the recording cycle within the recording cycle. Furthermore, in this embodiment, the effects of changes in the ambient temperature of the ink sheet and the ambient temperature of the heating element are also corrected at the same time.

In FIG. 9, 91 is a launch circuit, 92 is a recording signal generation circuit, 93 is a first temperature compensation signal generation circuit, 94 is a counter, 95 is a latch circuit, 96 is a second temperature compensation signal generation circuit, and 97 is a second temperature compensation signal generation circuit. The heating element drive circuit 98 is a read-only memory (hereinafter referred to as ROM).

The gradation data Dn of information to be recorded, the ink sheet ambient temperature Ta, and the heating element ambient temperature Tb are input to the ROM 9B. The ink sheet ambient temperature Ta and the heating element ambient temperature Tb are determined by the second temperature compensation signal generation circuit 96.
are also entered at the same time. ROM 9B is gradation data D
The pulse width twl of the recording signal and the pulse width tw2 of the heating change compensation signal corresponding to n and the ambient temperature Ta-Tb are stored, and the output consisting of a plurality of bits is connected to the latch circuit 91. When the launch circuit 91 receives the line timing signal LT, it temporarily stores this input information. The pulse width tw which is one output of the latch circuit 91
l is input to the recording signal generation circuit 92, and the other output, pulse width jw2, is input to the first temperature compensation signal generation circuit 93.

The recording signal generation circuit 92 receives the line timing signal Ll' and the clock signal CL, and outputs a recording signal to the heating element drive circuit 97. The first temperature compensation signal generation circuit 93 outputs a heating change compensation signal, a signal for compensating for heat storage fluctuations caused by changes in the amount of heating to the heating element, to the heating element driving circuit 97.

1 is input to the line timing signal LT and the clock signal M to the counter 94, and the line timing signal 1. Each time T is input manually, the numeric value is cleared and an addition operation is performed from the initial value in accordance with the clock signal C1. Therefore, the count value corresponds to the time interval between line timing signals LT. Latch circuit 95
When the line timing signal LT is input, the counter 94
81 value of -1↓↑g and the second temperature? ili compensation signal generation circuit output. Second temperature? The in compensation call signal generation unit 96 outputs to the heating element drive circuit 97 a cycle change compensation signal generated when the recording cycle is delayed by a predetermined time interval or more based on information from the latch circuit 95. The heating element driving circuit 97 applies a driving signal to the heating element of the man-malhesod to heat it. 9() corresponds to one heating element, so when the thermal head has 1680 heating elements, 1680 blocks 90
Requires.

FIG. 1θ shows the detailed circuit of FIG. The recording signal generation circuit 92 in FIG. 9 includes a delay circuit 921 and a timer 9.
22, the output of the latch circuit 91 is connected to the line 922, and the output of the timer 922 is connected to the heating element drive circuit 9.
7 is connected. The first temperature compensation signal generation circuit 93 consists of a delay circuit 931, a timer 932, a pulse generator 933, and an AND gate 8NDI.
The output of 1-ANDI is connected to a heating element drive circuit 97. The second temperature compensation signal generation circuit 96 is a ROM 961
・Timer 962 ・Composed of pulse generator 963 and AND gate AND2, output of launch circuit 95 ・Ink sheet ambient temperature Ta and heating element ambient temperature Tb are RO
Connected to M961. +1 (IM 961 stores the pulse width tw3 of the periodic change compensation signal, and the value of this pulse width by3 changes depending on the output value of the latch circuit 95 and the value of the ambient temperature Ta-Tb. AND gate A
The output of ND2 is connected to a heating element drive circuit 97.

The heating element drive circuit 97 includes an OR gate OR and a transistor T.
The output of the recording signal generation circuit 92, the output of the first temperature compensation signal generation circuit 93, and the output of the second temperature compensation signal generation circuit 96 are connected to the gate of the transistor Tr via an OR gate. . The drain of the L transistor is connected to the power supply Vcc, and its source is grounded via the heating element 73 of the thermal head.

Next, the operation of the circuit shown in FIG. 10 will be explained along the time chart shown in FIG. 11.

First, when the line timing signal LT arrives, the delay circuit 921 is activated, and the latch circuit 91 stores the pulse widths twl and tw2 from the ROM 98. At the same time, the line timing signal LT is sent to the counter 94,
Since the signal is input to the latch circuit 95 and the pulse generator 963, the count value of the counter 94 is cleared and addition is started from the initial value. The launch circuit 95 stores the count value of the counter 94 before being cleared and sends it to the ROM 961. The phase of pulse generator 963 is initialized by line timing signal LT. As described above, the ROM 961 sets the pulse width Koji 3 defined by the value from the launch circuit 95 and the ambient temperature Ta-Tb0 value in the timer 962. The output Sll of the timer 962 becomes '1'' from the time when the pulse width tw3 is set until the number of clock signals CL becomes equal to the pulse width tw3.

Therefore, the output S12 from the pulse generator 963 is gated by the output Sll in the AND gate ND2, and the output S12 of the heating element drive circuit 97 is output as the signal S13 (01?). is output to. This pulse width modulated periodic change compensation signal S13 drives the transistor Tr to heat the heating element 73, and at time t1, the temperature is changed to the target temperature T.
Let it be i.

When the delay time tdl has elapsed after the arrival of the line timing signal LT, the output S5 of the delay circuit 921 becomes '
Since the timer 922 starts counting the clock signal CL, the delay circuit 93[ is activated. In the timer 922, the ai of the clock signal CL
When the counting starts, the output S6 becomes "1", and the number of clocks that are counted is equal to the pulse width 1 from the latch circuit 91.
corresponds to "0". This output S6 is a recording signal and is sent to the husband register T via the or game 1-Of?
r is driven to heat the heating element 73.

This heating melts the ink on the ink sheet and transfers it to the recording paper, thereby performing recording.

The delay circuit g'31 sets its output S7 to "1°" after a predetermined delay time td2 has elapsed.The timer 932 is triggered by this signal S7 to start the clock signal CL's 4th cycle, and the pulse generator 933 The phase is initialized. When the timer 932 starts counting, its output S8 becomes '1°, and when the number of counted clocks corresponds to the pulse width tw2 from the launch circuit 91.
“0°.This output s8 is ant game L AND
At I, the output of the pulse generator 933 is gated, and at the AND gate aNn1, the pulse width modulated signal 510 is gated at the OR gate 01? Send to. This signal S10 is a heating change compensation signal, which compensates for the temperature of the heating element to reach the target temperature Ti at time t2 by heating the heating element 73 following the recording signal.

In this way, heat storage fluctuations caused by changes in the recording signal S6 applied to the heating element 73 are compensated by the heating change compensation signal S8, and the temperature of the heating element LJ at time t2 is adjusted.
The temperature of the heating element at time ti can be controlled so that the temperature of the heating element at time ti becomes the target temperature Ti by compensating for M thermal fluctuation of the heating element due to a change in the recording cycle using the cycle change compensation signal 513. .

Here, ROM 70a to ROM 7 in FIG.
0c or ROM 98・ROM in Figure 10
Consider the values that should be stored in 961.

The time-temperature characteristics of the heating element can be approximated by the following equation.

t: Time (time of application of drive signal is t=Q) 'T' (
t): Temperature of the heating element at time Tc: Ambient temperature (ambient temperature Tb of the heating element in the example of FIG. 10) T: Thermal time constant of the heating element LN: Pulse width of driving pulse W: Applied power [? (2) It shall be a counter-attack.

In addition, when LO≦t≦LA, the relationship between the temperature of the heating element and the recording density can be expressed by the following equation.

Td: Ambient temperature (Ambient temperature Ta of ink sheet 1 in the example of Fig. 10) llo: Saturation concentration C1: Ink transfer constant Q: Ink transfer barrier potential: Boltzmann constant Ch: Heat transfer from heating element to ink sheet If we take the constant for .

Therefore, ROM 70a "ROM" in FIG.
70 (: or ROM 98
- The value to be stored in the ROM 961 is determined by the above formula 5 and can be written in advance.

Next, the target temperature Ti will be considered. When the heat change compensation signal is used to compensate for fluctuations in heat storage caused by changes in the amount of heating, the temperature of the heating element can be increased by applying the heating change compensation signal, but cannot be decreased.

Therefore, the standard temperature Ti of the heating element at time t is the maximum gradation level, and a driving signal corresponding to χ·I is applied,
What is the time when temperature compensation is not performed? The temperature is set to a value equal to or higher than the temperature Tt of one body. In the embodiment, Ti-Tt is used, and therefore, when recording is performed by applying a drive signal corresponding to the maximum gradation level, heating by the heating change compensation signal is not performed.

The same applies to the case of compensating for fluctuations in heat storage due to changes in the recording cycle using a cycle change compensation signal, and the target temperature Ti is applied with a drive signal corresponding to the maximum gradation level.
Temperature Tt of the heating element that falls on time when temperature compensation is not performed
Set to a value equal to or higher than . In the embodiment, Ti=TL, and therefore, temperature compensation using the period change compensation signal is not performed for the shortest recording period.

In the above description, it has been assumed that in order to cancel out changes in the heating amount and recording period, the temperature of the heating element at a certain time should be a constant value T+ regardless of the heating amount and the recording period. This is due to the following reasons.

From equations fl) and (2), when t≧τ+ is -, arbitrary heating can be performed. When recording is performed with an arbitrary heating amount and recording cycle, it is sufficient to give the amplitude and time for each recording and add the equation (4).

. (e'' and I), so when recording is performed with an arbitrary heating amount and recording cycle, the difference between the heating element temperature T and the room temperature 'raO is proportional to C-17 for t≧τ''-Lw. and decrease. Therefore, if the temperature of the heating element at a certain time is a constant value Ti, then the temperature of the heating element at a subsequent time t becomes 'r(t),
All history such as heating amount and recording cycle will be deleted.

For the L<τ1 axis, the following theory holds: i) l It is necessary to pay attention to the following. By the way, when evaluating the heating element temperature Ti at a certain time, the difference of 1 "I" - 1 of the last applied drive signal is ζ with respect to the above time.
If it is before τ, there is no need to disclose past heating (eg, record laps, etc.).
If Shinji's rising edge J'' appears at the time 1- and is after that, then the rising edge time of the last applied drive signal τ
G4 The addition jJ% l'i
Ti must be set so that the error in the overall heating amount is minimized, taking into consideration the recording 101 and the recording 101.

12 to 16 are waveform diagrams of drive signals and time-temperature characteristic diagrams of a heating element according to the present invention.

In the example of FIGS. 12 and 13, one drive signal
This controls recording and temperature compensation. In FIG. 12, when the gradation level is dog, it is heated by the drive signal PA with the waveform shown at ta+, and when the gradation level is medium, it is heated by the drive signal PB with the waveform shown at fcl, and the gradation level is When the temperature is small, the temperature of the heating element at time L1 can be controlled to the target temperature Ti in any case by heating it with the drive signal 11c as shown in (d). Also,
When the start of the next recording is delayed until time L2 (by heating with the drive signal Pa as shown in bl), recording is performed at the same gradation level as the gradation level caused by the drive signal PA, and at the time t
The temperature of the heating element in step 2 can be controlled to the target temperature Ti. Note that the waveform of the drive signal shown at te+ is fd
The waveform of the drive signal corresponding to the drive signal 1 is constructed by pulse width modulation. FIG. 13 shows an example in which the pulse width and voltage value of the drive signal are changed. When the gradation level is small, heating is performed by the drive signal PA having a waveform as shown in fdl, and the floors, Il, I...・When Ru is a dog (bl 6.9
The temperature of the heating element at time E1 can be controlled to the target temperature Ti in any case by applying the pulse-like waveform of the drive signal 1111 to the control P1. Furthermore, when the start of the next recording is delayed until time L2 (by heating with the drive signal 11b as shown in [driving signal 1]) recording of the same gradation AI!J as the gradation of 0 is performed. The temperature of the heating element at t2 can be controlled to Ti.

Figures 14 and 15 are examples in which compensation for heat storage fluctuations due to changes in recording and heating amount is performed using one drive signal, and compensation for heat storage fluctuations due to period changes is performed using another drive signal. It is. In FIG. 14, when the gradation level is high, the temperature of the heating element is set to Ti at time L1 each time it is heated by the drive signal 11A as shown in fa), and when the next recording start is delayed until time L2, (b
As shown in FIG. 1, the temperature of the heating element at time t2 is controlled to Ti by heating the heating element using the periodic change compensation signal pa following the drive signal PA. When the gradation level is small, the temperature of the heating element is set to T at time t1 by heating the heating element with a drive signal PR having a waveform as shown in icl.
i, and when the start of the next recording is delayed until time t2, the temperature of the heating element at time t2 is set to Ti by applying the period change compensation signal pb following the drive signal PB as shown in fdl. I can do it.

The example in FIG. 15 differs from the example in FIG. 14 only in that both the drive signals PA and PB and the periodic change compensation signals pa-pb use pulse width modulated signals, and the drive signal 1)
8. While recording by PB, it compensates for fluctuations in heat storage due to changes in heating amount, and generates a periodic change compensation signal pa-
What about fluctuations in the heat storage of the heating element due to changes in the recording cycle due to pb? The points of compensation are the same as in the example of FIG.

FIG. 16 shows an example in which a single temperature compensation signal is used to compensate for fluctuations in heat storage due to changes in the amount of heating and fluctuations in heat storage in the heating element due to changes in the recording cycle. That is, by recording with the recording signal P and applying the heating change compensation signal p as shown in (al), the temperature of the heating element at time t1 is set to Ti, and the heat storage fluctuation of the heating element due to the change in the amount of heating is Compensate for the periodic change?+Ii l1li signal pp
By applying Ti, the temperature of the heating element at time t2 is set to Ti, thereby compensating for the M heat fluctuation of the heating element caused by the change in the recording cycle.

On the other hand, as shown in (b), if recorded using the recording signal P, the temperature at time Ll? ili without making amends;
Thereafter, by applying the temperature compensation signal II Ilp, the temperature at time (2) is set to Ti, and the fluctuations in heat storage due to changes in the amount of heating and the fluctuations in heat storage due to changes in the recording cycle are calculated at this temperature. Compensation is performed simultaneously from the compensation signal pppG.

fg) Effects of the Invention As described above, according to the present invention, the heating amount of the drive signal for heating the heating element is determined by the information to be recorded, and
The conditions for applying the drive signal are set so that the temperature of the heating element at the end of recording is equal to the temperature of the heating element at the start of recording. It is possible to eliminate fluctuations in heat storage. Therefore, the conditions of the drive signal can be defined only by the information to be recorded, and the conventional complicated four steps can be omitted. As a result, the amount of heating can be controlled with high precision,
Moreover, the recording speed can be easily improved.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the configuration of a thermal transfer printer, Figure 2 is a cross-sectional view of the thermal head, Figure 3 is a diagram of drive waveforms and time-temperature characteristics of the heating element when temperature compensation is not performed, and Figure 4 is heating The drive signal waveform and the time-temperature characteristic diagram of the heating element when the temperature of the heating element is compensated by the change compensation signal. Figure 5 shows the drive signal waveform and the heating element when the temperature of the heating element is compensated by the periodic change compensation signal. 6 to 8 show the first embodiment of the present invention, FIG. 6 is a block diagram, and FIG.
The figure is a detailed circuit diagram, Figure 8 is a time chart, Figures 9 to 11 show a second embodiment of the present invention, Figure 9 is a block diagram, Figure 10 is a detailed circuit diagram, and Figure 11 is a block diagram. 12 is a time chart, and FIGS. 12 to 16 are waveform diagrams of drive signals of the present invention and time-temperature characteristic diagrams of a heating element. In the figure, 11 is a thermal head, 12 is an ink sheet, 1
3 is recording paper, 23 and 73 are heating elements, s2 and s6 are recording signals, S4 and SIO are heating change compensation signals, St, S]
3 indicates a periodic change compensation signal. Fig. 1 Fig. 21 Fig. 11 Fig. 12 g 13 Fig. 75＼ Tomo ■ 1. Vinegar, t2 Heiha ■ 11-kun 72 “ (0) ” u ” 1 1 Self Fig. 15 Fig. 161! 1

Claims (1)

[Scope of Claims] ('') A thermal printer's driving method, characterized in that in a thermal printer that performs recording by heating a heating element in response to a drive signal, the drive signal is controlled to be driven. (2) The drive signal consists of a recording signal and a temperature compensation signal, the recording signal is defined by the density information to be recorded, and the temperature compensation m is set to L at any time after the application of the recording signal ends. Claim (1) characterized in that the temperature of the heating element (-) is controlled to a predetermined value.
The thermal head drive method described in ). (3) The temperature compensation signal consists of a heating change compensation signal and a periodic change compensation signal, and the heating change compensation signal indicates that the temperature of the heating element at a certain time after the end of the application of the recording sweat is the temperature of the heating element at the start of recording. Compensate for the temperature fluctuations of the heating element heated by the recording signal by controlling it to be equal to the periodic change? The li signal is controlled so that the temperature of the heating element at an arbitrary time after the end of application of the recording signal is equal to the temperature of the heating element at the start of recording, so that the temperature of the heating element due to changes in the recording cycle is controlled. The thermal head drive method according to claim (2), characterized in that fluctuations are compensated for.